FPM-Zebra interactions and EVPN MAC route handing

[Syed Hasan Raza Naqvi]

Hi,

I have below queries related to Zebra-FPM interaction and EVPN MAC handling
in FRR. Would appreciate if someone could answer.


(1)  First of all, I don't see any communication from Fpm to Zebra today.
The code in Zebra just de-queues from the fpm socket and discards.
    zebra_fpm.c:zfpm_read_cb() ...
/*
* Just throw it away for now. */
    Wondering if we never had a situation where specific info or feedback
is required from Fpm?
    For example, the route installation errors in Fpm communicated back to
Zebra?


(2) This question is related to above. In systems where L2
forwarding/learning is achieved in hardware (asic) forwarding plane, not
all of the MACs will be available in Linux FDB. Only the MACs which were
learned due to ARP/ND would be present in Linux FDB.

    In such a case, it might be better to inject the local MACs into Zebra
directly from Fpm. But looks like the only way for local MACs to be
advertised into EVPN is to somehow inject  them into Linux FDB and let
Zebra learn from Linux.

    Is this correct understanding? And will it be acceptable to introduce a
knob in zebra to get the local MACs from Fpm instead of Linux FDB?


(3) On the similar lines as above, not all of the remote EVPN MACs need to
be present in Linux FDB. Only those MACs which have corresponding IP
(ARP/ND) are required in Linux FDB. In such a case, it might be better to
selectively install MACs into Linux, and send all of the EVPN MACs to Fpm
so that they can be installed in asic. But I don't see zebra gives any MAC
to Fpm. I would like to hear the rationale behind this as well. And is it a
good idea to introduce a knob in Zebra to achieve it?

Thanks in advance!

Regards,
Hasan
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